2023 day1 naive solution

2023/day1.exs

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+defmodule Day1 do
+  def part1(input) do
+    input
+    |> Enum.map(fn line ->
+      numbers = String.replace(line, ~r/[^1-9]/, "")
+      String.to_integer(String.first(numbers) <> String.last(numbers))
+    end)
+    |> Enum.sum()
+  end
+
+  def part2(input) do
+    input
+    |> Enum.map(fn line ->
+      numbers =
+        line
+        |> string_to_digits()
+        |> String.replace(~r/[^1-9]/, "")
+
+      String.to_integer(String.first(numbers) <> String.last(numbers))
+    end)
+    |> Enum.sum()
+  end
+
+  def string_to_digits(line) do
+    line
+    |> String.replace("one", "o1e")
+    |> String.replace("two", "t2o")
+    |> String.replace("three", "t3e")
+    |> String.replace("four", "f4r")
+    |> String.replace("five", "f5e")
+    |> String.replace("six", "s6x")
+    |> String.replace("seven", "s7n")
+    |> String.replace("eight", "e8t")
+    |> String.replace("nine", "n9e")
+  end
+
+  def input do
+    with [input_filename] <- System.argv(),
+         {:ok, input} <- File.read(input_filename) do
+      String.split(input, "\n", trim: true)
+    else
+      _ -> :error
+    end
+  end
+
+  #######################
+  # HERE BE BOILERPLATE #
+  #######################
+
+  def run do
+    case input() do
+      :error -> print_usage()
+      input -> run_parts_with_timer(input)
+    end
+  end
+
+  defp run_parts_with_timer(input) do
+    run_with_timer(1, fn -> part1(input) end)
+    run_with_timer(2, fn -> part2(input) end)
+  end
+
+  defp run_with_timer(part, fun) do
+    {time, result} = :timer.tc(fun)
+    IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
+    IO.puts("#{result}\n")
+  end
+
+  defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
+  defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
+  defp format_time(μsec), do: "#{μsec / 1_000_000}s"
+
+  defp print_usage do
+    IO.puts("Usage: elixir day1.exs input_filename")
+  end
+end
+
+Day1.run()